Chamberlain



May 28, 1957 J. cHAMBl-:RLAIN 2,'94Q114 PORTABLE ELECTRIC BATTERY LAMPS Filed May 25, 1954 l 5 Sheets-Sheet l Y By ltorney J. CHAMBERLAIN 2,794,114

PORTABLE ELECTRIC BATTERY LAMPS.

3 Sheets-Sheet 2 May Z8, '1957 Filed Mz'ay 2, 1954 #ff-3s* wu, MM By www Attorney 5 Sheets-Sheet 3 Filed May 25, 1954 In ventr ttorney 2,794,114 PORTABLE ELECTRIC BATTERY LAMPS near Manchester, England,

John Chamberlain, Denton,

near Manassignor to Qldham & Son Limited, Denton, chester, England, a British company This invention relates to portable electric battery lamps.

Such lamps nd a particular use as miners electric cap lamps, and may be used in atmospheres containing explosive gases such as methane. Such cap-lamps contain a bulb which usually has a tungsten lilament. If the caplamp is in use and the bulb envelope is broken, exposing the glowing tungsten iilament to the explosive atmosphere, a `great danger of explosion arises. v

It has heretofore been proposed to mount the bulb in a miners :cap-lamp upon an arm and to spring urge the bulb away from its contact so that the bulb envelope bears against the lens glass of the lamp. If the lens glass or bulb envelope of such a cap-lamp is broken, the bulb base is moved forward by the spring from a live contact, so that current is cut off from the bulb. Under normal conditions of breakage, this is suiiicient to prevent ignition of an explosive atmosphere surrounding the lamp.

If, however, the tungsten iilament of the bulb remains intact after breakage of the lens glass and bulb envelope, the filament may continue to `glow if the bulb base is prevented frorn moving forward for any reason, for example, if the bulb envelope and lens glass are only partially broken, or if the bulb is crushed back into the lamp casing. The exposure of a glowing filament to an explosive atmosphere gives rise to a danger of explosion as explained above.

A main object of the invention is to provide a construction of a lamp in which the bulbs are surrounded by a non-combustion supporting gas.

A subsidiary object is to provide a construction of lamp in which, upon damage to the lamp which might expose the filament of the bulb to an explosive atmosphere, the supply of current to the bulb is yeffectively cut off, even if 4the iilament remains intact.

A portable electric battery lamp construction according to the invention comprises a lamp body which includes an hermetically sealed lamp chamber lled with a noncombustion supporting gas under pressure and having a lens glass, a reilector, bulb holder and bulb, and a pressure-sensitive switch in circuit with the bulb which is disposed to respond to the gas pressure in the interior of the lamp unit, and which operates to cut oif the flow of electric current to the bulb upon a predetermined fall of pressure within the lamp chamber. By such arrangement an additional vfactor of safety is incorporated.

In a preferred embodiment, in which a fuse is in circuit with the bulb and battery, the pressure-sensitive switch is in parallel with the bulb in a circuit through the battery and fuse, and upon the predetermined fall of pressure within the lamp chamber, completes this latter circuit whereby the fuse is blown and current cut olf from the bulb.

Alternatively, the pressure-sensitive switch may be in circuit with the bulb and battery, and operate to break this circuit, upon the predetermined fall of pressure within the lamp chamber.

The invention also extends to an hermetically sealed lamp unit for such a portable electric battery lamp.

" nited States Patent() rial, such as beryllium copper or phosphor bronze. The' 2,794,114 Patented May 28, 1957 "ice In order that the invention may be better understood, preferred embodiments thereof will now be described by Way of example, with referenceto the accompanying drawings, in which:

Figure 1 is a cross-section of a lamp according to the invention,

Figure 2 is a section on the lines lI-II of Figures 1 and 3,

Figure 3 is a front view of the lamp body shown in Figures 1 and 2 with the bulbs, reector and lens glass removed, v

Figure 4 is a circuit diagram of the complete cap lamp and battery,

. Figure 5 shows an alternative form of bulb holder, and

Figure 6 shows a further form of bulb holder and an alternative seal for the lens glass and reliector.

In the several iigures of the drawings, like numerals designate like parts.

The cap lamp shown in Figures l, 2 and 3, comprises an hermetically sealed lamp chamber A which includes a lens glass 1, a reflector 2 and a main bulb 3. The lamp chamber is iilled with a non-combustion supporting gas such as nitrogen, carbon dioxide, argon or neon, under pressure. A pressure sensitive switch S is in communication with the interior of the lamp chamber A and operates to cut off the llow of electric current to the bulb 3 upon a predetermined fall of pressure within the lamp chamber.

The lens glass 1 is bevelled at 4 on its front peripheral edge and is held in position by a similarly bevelled lip of a bezel ring 5 bearing on the bevelled portion 4. The bezel ring has kanrinternallyv threaded skirt 6 which is engaged upon an-annular member 7, which bears against an overhanging lip 8 ofthe reflector 2. This lip 8 is grooved to receive a'ring 9 of resilient material, in this case a toroidally shaped O ring of rubber or other resilient material, which is free from sulphur or other silver tarnishing agents. vWhen the annular member 7 is screwed into the skirtof the bezel ring 5, an hermetic seal is formed between the reflector and the lens glass.

The reflector carries two bulb-holders, the main bulbholder and the pilot bulb-holder. The main bulb-holder comprises a tubular member 10, Figure 2, secured in the centre of the reiiector 2 and internally screwthreaded at 11 to receive the external contact 12 of the main bulb 3. The outer end of the tubular member 10 is closed by an electrical-insulating closure 13 of ceramic material. The ceramic closure is metallized around its periphery and a soldered joint is made between the metallised periphery and the tubular member 10. A lead-in wire 14 passes through the closure 13 and is soldered to a metallised oriice in the closure. Within the tubular member 10 and between the screwthreaded portion 11 andthe closurel 13 is an electrical-insulating sleeve y15 surrounding a compression spring16 carrying a Contact 17 for the central Contact 18 of the bulb 3. The contact 17 is connected to the lead-in wire 14 by a tlexible connection 19. The compression spring 16 holds the bulb against the s-crewthread of the bulb holder and thus prevents movement of the bulb due to vibration. Moreover, the bulb may be focussed by vscrewing it into, or out of, the bulb holder.

The holder for the pilot bulb 20, Figure l, is similar to the main bulb holder and is secured in a cylindrical recess 21 in the reector to one side of the main bul-b holder. The bulb holdersy are disposed within an electrical-insulating housing V22.

The pressure-sensitive switch VS comprises an aneroid capsule 23, Figure l, mounted on a tube 2.4 secured on the tubular member 10 and providing communication between the interior of the lamp unit A and the capsule. The aneroid capsule has a diaphragm 25 of resilient mate- 3 diaphragm carries a movable contact 26 which co-operates with a Xed contact 27 within the capsule. The electrical connection to the contact 27 passes through a mctallised ceramic insert 28 soldered into the capsule wall.

A non-combustion supporting gas which is inert to silver is introduced into the lamp chamber through a filler plug F, Figure 2. The filler plug is mounted on the tubular member and is of substantially V-shape. An orice 29 connects the hollow limbs of the V with the interior of the lamp unit. One of the limbs is internally screwthreaded to receive a plug 30 carrying a resilient insert 31 at its end to close the orifice 29. Gas under pressure is introduced through the other limb 32. The` plug 30 isunscrewed and gas owsinto the lamp chamber. When sufcient gas has been admitted tothe lamp, the plug 30 is screwed down so that the resilient insert 31 closes the orifice 29 to prevent the escape of gas.

Each of the lead-in wires 14 of the two bulb holders is connected to one of two spaced contacts 33, 34, Figures 2 and 3 on a bridge piece 35 forming part of the housing 22. The xed contact 27 of the pressure-sensitive switch is connected to a spring arm 36, Figure 1.

The sealed lamp chamber A is secured in a lamp body B by three screws 37 which pass through bores in the body and engage threaded holes in the annular member 7 which is of metal. A flexible connection 38 from the battery 39 passes through an aperture in the lamp body, and one lead 40 is connected to one of the screws 37 and thus through the annular member 7 to the reilector 2. The other lead 41 is connected to a terminal 42 disposed in the body B. When the chamber A is in position in the body, the spring arm 36 bears against the terminal 42. A further connection is taken from the terminal 42 to a spring arm 43. The spring arm is secured to one end in the lamp body B and at the other end is slotted to receive a nut 44 having a peripheral groove with curved Ifaces which engage the opposite faces of the arm 43, as shown in Figure 3. The nut 44 is engaged on a threaded member 45 rotatable by means of an electrical insulating knurled knob 46 on the outside of the body 36. The transversesection of the nut 44 at the plane of the groove is square and the nut is prevented from rotating by the location of this square section in the rectangular slot in the arm 43. The arm 43 has a central contact 47 which is disposed between the spaced contacts 33, 34 of the lamp cham'ber'when the chamber is disposed in the body B. The terminal 42 is also connected to a spring charging terminal 48, Figure l, which is provided with `a lock for protection similar to that described in the specification of U. S. application Serial No. 376,097, now Patent No. 2,772,924.

The battery 39 is connected to one of the leads of the exible connection 38 through its fuse 49. The fuse 49 is of the sealed type and is disposed Within the battery lid 50 so as to lbe in accessible normally.

The surface of the reilector is of unlacquered silver. This is advantageous as silver has the highest reflectivity coefficient of all metals. Normally silver is unsuitable for this purpose because it tarnishes due to the formation of a layer of silver sulphide on its surface. Tarnishing is prevented in the present construction `as the rellector is hermetically sealed from sulphiding agents. In order to prevent the bezel ring 5 cutting off light from the bulb, the internal diameter of this ring is chosen so that light from the main bulb 3 which avoids reflection by the rellector by passing just clear of the internal diameter of the lip 8 of the reflector is refracted to pass out of the front of the lens `glass 1 just clear of the internal diameter of the bezel ring.

The surface of the cylindricalrecess 21 is made reflecting in the same manner as the surface of the reector 2, i. e. by silvering, in order to avoid loss of light from the main bulb or pilot bulb when this latter is in use.

In use, the main bulb is illuminated by turning the knob 46 until the spring arm 43 has moved with its contact 47 into engagement with the contact 34. A circuit is then completed, Fig. 4, from one side of the battery 39 through the fuse 49, the reflector 2, the main 4bulb 3 and the spring arm 43 to the other side of the battery. If for any reason, the hermetically sealed unit is broken or damaged in such a way as to release the gas under pressure, the diaphragm of the pressure sensitive switch will move inwardly until the contacts 26 yand 27 engage, whereupon a heavy current will ow through the short circuit across the battery and fuse, causing the latter to blow and leaving the lamp connections dead.

Experiments have shown that the time taken for the pressure-sensitive switch to operate after the lens glass has been broken is of the order of one thousandth of a second. During this time, the non-combustion supporting gas under pressure in the lamp chamber willbe escaping and preventing the entry of inammable gas into the lamp unit until all danger of sparking is passed, While the lilamentof the bulb will be cooled rapidly.

If it is desired to use the pilot bulb 20, the knob 46 is rotated in the opposite direction until the contact 47 on the spring arm 43 is in engagement with the contact 33. A circuit is then completed from one side of the battery through the fuse, reector, pilot bulb and spring arm to the other side of the battery.

In an alternative construction, illustrated in Figure 5, the end of the bulb holder 18 is closed by a circular plate 51 and the lead-in wire 14 passes through a ceramic insert 52 in the side wall of the holder. The spring 16 urging the contact 17 into engagement with the contact 18 of the bulb is housed in an electrical insulating cup member 53.

The lens glass 1 may be permanently secured to the reflector 2, as shown in Figure 6. In this case, a ring of sprayed aluminium is deposited around the edge of the lens glass, followed by a sprayed ring of copper deposited over the aluminium. The lens glass is then soldered into the reflector by means of a tin-lead, tinlead-silver or other suitable soldering alloy. Access to the interior of the lamp chamber is provided by a removable bulb holder 54. This, instead of being Xed to the reflector, is screwed into a nut member 55 mounted on a reflector and is sealed by an annular sealing member 56.

The surface of the reflector may be modied for example, by mechanically roughening, as by shot blasting the surface, and then depositing a layer of silver by vacuum evaporation.

TheY annular member 7 on which the bezel ring 5 is secured may be Xed to or integral with the lamp body B, so that the lens glass and bezel ring may be removed to give access to the bulbs without removing the whole lamp unit. In this case the filler plug must be accessible from outside and may be concealed behind the caphook 57.

The constructions described are particularly safe for use in atmospheres containing explosive gases, and a high proportion of the light produced by the bulb is given out by the lamp. Further the lamps are sealed against the entry of dust, water or dirt, so that they will not be effected by the adverse conditions in which they aroused.

I claim:

l. A portable electric battery lamp comprising a hemispherical member formed of non-conducting material and a closing member for the same, the hemispherical member having a lamp socket secured therein, the closing member comprising a cap having its interior screw threaded at one side and having a metal ring screw threaded into the cap, the other side of he cap having aninwardly extending bevel, a lens having its periphery beveled and engageable by the bevel on the cap, a metal rellector having its edge engaged between the ring and the lens, a. resilient member engaging between the re- Hector and the lens to provide a seal therefor, a plurality of bolts extending through openings in the hemispherical member and screw threaded into the metal ring to hold the parts together, a resilient seal being positioned between the ring and the edge of the hemispherical member to provide a gas tight seal therebetween, a tube extending into the side of the lamp socket having means thereon for supplying an inert gas under pressure to the inside of the lamp socket, a lamp in the lamp socket, and in contact with the metal reilector, a battery, a conductor from the battery to one of the bolts and to the side of the lamp, another conductor from the battery to a Contact on the bottom of the lamp, a fuse in the conductor, an aneroid capsule having a diaphragm thereon and secured to the outside of the lamp socket, the inside of the capsule being in communication with the interior of the lamp socket, a xed contact, a contact on the diaphragm movable to engage the fixed contact, wires connecting said contacts in circuit with the battery and the use, whereby when said contacts are brought together the fuse will be blown and the bulb extinguished.

2. The invention as claimed in claim 1 wherein two bulbs are mounted in the hemispherical member and a switch is provided with operating means for selectively lighting either of the bulbs.

3. The invention as claimed in claim 1 wherein the reflector is coataed with unlacquered silver.

References Cited in the le of this patent UNITED STATES PATENTS 459,872 Tommasi Sept. 22, 1891 1,833,318 Daloz Nov. 24, 1931 2,165,194 Wilbur July 4, 1939 2,304,085 Griffin Dec. 8, 1942 2,312,614 Wheat Mar. 2, 1943 2,423,664 Ryder July 8, 1947 2,517,478 Griin Aug. 1, 1950 

